scholarly journals Adrenergic inhibition of branched-chain 2-oxo acid dehydrogenase in rat diaphragm muscle in vitro

1983 ◽  
Vol 216 (1) ◽  
pp. 63-70 ◽  
Author(s):  
T N Palmer ◽  
M A Caldecourt ◽  
M C Sugden
Keyword(s):  
Cyclic Amp ◽  
Tricarboxylic Acid Cycle ◽  
Diaphragm Muscle ◽  
Dibutyryl Cyclic Amp ◽  
Adrenergic Agents ◽  
Acid Dehydrogenase ◽  
14Co2 Production ◽  
Branched Chain ◽  
Tricarboxylic Acid Cycle Intermediates

In theory, the complete oxidation to CO2 of amino acids that are metabolized by conversion into tricarboxylic acid-cycle intermediates may proceed via their conversion into acetyl-CoA. The possible adrenergic modulation of this oxidative pathway was investigated in isolated hemidiaphragms from 40 h-starved rats. Adrenaline (5.5 microM), phenylephrine (0.49 mM) and dibutyryl cyclic AMP (10 microM) inhibited 14CO2 production from 3 mM-[U-14C]valine by 35%, 28% and 19% respectively. At the same time, these agents stimulated glycogen mobilization (measured as a decrease in glycogen content) and glycolysis (measured as lactate release). Adrenaline, phenylephrine and dibutyryl cyclic AMP did not inhibit 14CO2 production from 3 mM-[U-14C]aspartate or 3 mM-[U-14C]glutamate, although, as in the presence of valine, the agents stimulated glycogen mobilization and glycolysis. The rate of proteolysis (measured as tyrosine release in the presence of cycloheximide) was not changed by adrenaline. The data indicate that the adrenergic inhibition of 14CO2 production from [U-14C]valine was not a consequence of radiolabel dilution. Inhibition was apparently specific for branched-chain amino acid metabolism in that the adrenergic agonists also inhibited 14CO2 production from [1-14C]valine, [1-14C]leucine and [U-14C]isoleucine. Since 14CO2 production from the 1-14C-labelled substrates is a specific measure of decarboxylation in the reaction catalysed by the branched-chain 2-oxo acid dehydrogenase complex, it is at this site that the adrenergic agents are concluded to act.

scholarly journals Effects of insulin on the pattern of glucose metabolism in the perfused working and Lagendorff heart of normal and insulin-deficient rats

1969 ◽  
Vol 115 (3) ◽  
pp. 537-546 ◽  
Author(s):  
E B Chain ◽  
K. R. L. Mansford ◽  
L. H. Opie
Keyword(s):  
Glucose Metabolism ◽  
Tricarboxylic Acid Cycle ◽  
Work Load ◽  
Tricarboxylic Acid ◽  
Diaphragm Muscle ◽  
Perfusion Fluid ◽  
Acid Cycle ◽  
14Co2 Production ◽  
Tricarboxylic Acid Cycle Intermediates ◽  
Phosphorylated Sugars

1. The metabolic pattern of [U−14C]glucose in the isolated rat heart has been studied, with both retrograde aortic (Langendorff) and atrially (working) perfused preparations in the presence and absence of insulin, in normal animals, animals rendered insulin-deficient (by injection of anti-insulin serum 1hr. before excision of the heart) and animals rendered diabetic by streptozotocin injection 7 days before use. 2. Radioautochromatograms of heart extracts show that the pattern of glucose metabolism in heart muscle is more complex than in diaphragm muscle. In addition to 14CO2, glycogen, oligosaccharides, phosphorylated sugars and lactate (the main metabolites formed from [14C]glucose in diaphragm muscle), 14C label from [14C]glucose appears in heart muscle in glutamate, glutamine, aspartate and alanine, and in tricarboxylic acid-cycle intermediates. 3. By a quantitative scanning technique of two-dimensional chromatograms it was found that a mechanical work load stimulates glucose metabolism, increasing by a factor of 2–3 incorporation of 14C into all the metabolites mentioned above except lactate and phosphorylated sugars, into which 14C incorporation is in fact diminished; 14CO2 production is equally stimulated. 4. Addition of insulin to the perfusion fluid of the working heart causes increases in 14C incorporation, by a factor of about 1·5 into 14CO2, by a factor of about 3–5 into glycogen, lactate and phosphorylated sugars, by a factor of about 2–3 into glutamate and tricarboxylic acid-cycle intermediates and by a factor of about 0·5 into aspartate, whereas incorporation into alanine and glutamine is not affected. The effect of a work load on the pattern of glucose metabolism is thus different from that of insulin. 5. Increasing the concentration of glucose in the perfusion fluid from 1 to 20mm leads to changes of the pattern of glucose metabolism different from that brought about by insulin. 14CO2 production steadily increases whereas [14C]lactate and glycogen production levels off at 10mm-glucose, at values well below those reached in the presence of insulin. 6. In Langendorff hearts of animals rendered insulin-deficient by anti-insulin serum or streptozotocin, glucose uptake, formation of 14CO2 and [14C]lactate, and 14C incorporation into glycogen and oligosaccharides are decreased. In insulin-deficient working hearts, however, glucose uptake and 14CO2 production are normal, whereas incorporation of 14C into glycogen and [14C]lactate production are greatly decreased. 7. Insulin added to the perfusion fluid restores 14C incorporation from glucose into 14CO2, glycogen and lactate in the Langendorff heart from animals rendered insulin-deficient by anti-insulin serum; in hearts from streptozotocin-diabetic animals addition of insulin restores 14C incorporation into glycogen and lactate, but 14CO2 production remains about 50% below normal. 8. The bearing of these results on the problem of the mode of action of insulin is discussed.

scholarly journals Amino acid oxidation and alanine production in rat hemidiaphragm in vitro. Effects of dichloroacetate

1984 ◽  
Vol 223 (1) ◽  
pp. 113-117 ◽  
Author(s):  
T N Palmer ◽  
M A Caldecourt ◽  
M C Sugden
Keyword(s):  
Amino Acids ◽  
Pyruvate Dehydrogenase ◽  
Tricarboxylic Acid Cycle ◽  
Acid Oxidation ◽  
14Co2 Production ◽  
In Vitro Effects ◽  
Tricarboxylic Acid Cycle Intermediates ◽  
Rate Limiting ◽  
Main Carbon

Dichloroacetate (an activator of pyruvate dehydrogenase) stimulates 14CO2 production from [U-14C]glucose, but not from [U-14C]glutamate, [U-14C]aspartate, [U-14C]- and [1-14C]-valine and [U-14C]- and [1-14C]-leucine. It is concluded (1) that pyruvate dehydrogenase is not rate-limiting in the oxidation to CO2 of amino acids that are metabolized to tricarboxylic acid-cycle intermediates, and (2) that carbohydrate (and not amino acids) is the main carbon precursor in alanine formation in muscle.

scholarly journals Glycolytic origin of alanine formed in rat diaphragm muscle in vitro

1985 ◽  
Vol 231 (3) ◽  
pp. 801-804 ◽  
Author(s):  
M A Caldecourt ◽  
D J Cox ◽  
M C Sugden ◽  
T N Palmer
Keyword(s):  
Amino Acids ◽  
De Novo ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Diaphragm Muscle ◽  
Rat Diaphragm ◽  
Acid Cycle ◽  
Tricarboxylic Acid Cycle Intermediates ◽  
Alanine Production

In quarter-diaphragms from 40 h-starved rats the rate of glycogen mobilization is sufficient to account for the rate of lactate+pyruvate+alanine production. It is concluded, therefore, that alanine derives its carbon skeleton predominantly via glycolysis and not via synthesis de novo from tricarboxylic acid-cycle intermediates and related amino acids.

The inhibitory effects of some adenosine nucleolipids on the lipolysis in rat epididymal fat pads in vitro

1979 ◽  
Vol 44 (5) ◽  
pp. 1651-1656 ◽  
Author(s):  
Sixtus Hynie ◽  
Jiří Smrt
Keyword(s):  
Fatty Acids ◽  
Cyclic Amp ◽  
Dibutyryl Cyclic Amp ◽  
Inhibitory Effects ◽  
Epididymal Fat ◽  
Fat Pads

3'-Oleolyl-2,3-dihydroxypropyl-AMP, 3'-stearoyl-2,3-dihydroxypropyl-AMP, octadecyl-AMP and palmitamidoethyl-AMP inhibited in comparison with adenosine or fatty acids much stronger the lipolysis in rat epididymal fat pads in vitro stimulated by isoproterenol, theophylline and dibutyryl cyclic AMP. The inhibition of the effects of the two latter drugs suggest that the described effect is caused not only by the inhibition of the cyclic AMP production but also by the inhibition of its effect on the following steps in process of lipolysis.

scholarly journals Reversible ATP-induced inactivation of branched-chain 2-oxo acid dehydrogenase

1980 ◽  
Vol 192 (1) ◽  
pp. 155-163 ◽  
Author(s):  
R Odessey
Keyword(s):  
Skeletal Muscle ◽  
Liver Mitochondria ◽  
Initial Activity ◽  
Rat Skeletal Muscle ◽  
Kidney Mitochondria ◽  
Physiological Conditions ◽  
Acid Dehydrogenase ◽  
Skeletal Muscle Mitochondria ◽  
Branched Chain

The branched chain 2-oxo acid dehydrogenase from rat skeletal muscle, heart, kidney and liver mitochondria can undergo a reversible activation-inactivation cycle in vitro. Similar results were obtained with the enzyme from kidney mitochondria of pig and cow. The dehydrogenase is markedly inhibited by ATP and the inhibition is not reversed by removing the nucleotide. The non-metabolizable ATP analogue adenosine 5′-[beta gamma-imido] triphosphate can block the effect of ATP when added with the nucleotide, but has no effect by itself, nor can it reverse the inhibition in mitochondria preincubated with ATP. These findings suggest that the branched chain 2-oxo acid dehydrogenase undergoes a stable modification that requires the splitting of the ATP gamma-phosphate group. In skeletal muscle mitochondria the rate of inhibition by ATP is decreased by oxo acid substrates and enhanced by NADH. The dehydrogenase can be reactivated 10-20 fold by incubation at pH 7.8 in a buffer containing Mg2+ and cofactors. Reactivation is blocked by NaF (25 mM). The initial activity of dehydrogenase extracted from various tissues of fed rats varies considerably. Activity is near maximal in kidney and liver whereas the dehydrogenase in heart and skeletal muscle is almost completely inactivated. These studies emphasize that comparisons of branched chain 2-oxo acid dehydrogenase activity under various physiological conditions or in different tissues must take into account its state of activation. Thus the possibility exists that the branched chain 2-oxo acid dehydrogenase may be physiologically regulated via a covalent mechanism.

scholarly journals Metabolic phases during the development of granulation tissue

1967 ◽  
Vol 105 (1) ◽  
pp. 333-341 ◽  
Author(s):  
Kirsti Lampiaho ◽  
E. Kulonen
Keyword(s):  
Granulation Tissue ◽  
Collagen Synthesis ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Pentose Phosphate ◽  
Acid Cycle ◽  
Short Period ◽  
Tricarboxylic Acid Cycle Intermediates ◽  
Observation Period

1. The metabolism of incubated slices of sponge-induced granulation tissue, harvested 4–90 days after the implantation, was studied with special reference to the capacity of collagen synthesis and to the energy metabolism. Data are also given on the nucleic acid contents during the observation period. Three metabolic phases were evident. 2. The viability of the slices for the synthesis of collagen was studied in various conditions. Freezing and homogenization destroyed the capacity of the tissue to incorporate proline into collagen. 3. Consumption of oxygen reached the maximum at 30–40 days. There was evidence that the pentose phosphate cycle was important, especially during the phases of the proliferation and the involution. The formation of lactic acid was maximal at about 20 days. 4. The capacity to incorporate proline into collagen hydroxyproline in vitro was limited to a relatively short period at 10–30 days. 5. The synthesis of collagen was dependent on the supply of oxygen and glucose, which latter could be replaced in the incubation medium by other monosaccharides but not by the metabolites of glucose or tricarboxylic acid-cycle intermediates.

TESTOSTERONE SECRETION BY FOETAL RAT TESTES IN VITRO

1976 ◽  
Vol 71 (2) ◽  
pp. 231-238 ◽  
Author(s):  
RÉGINE PICON
Keyword(s):  
Cyclic Amp ◽  
Synthetic Medium ◽  
Functional Differentiation ◽  
Dibutyryl Cyclic Amp ◽  
Testosterone Secretion ◽  
Testosterone Production ◽  
Foetal Rat

SUMMARY Testosterone secretion by foetal rat testes (13½–21½ days of gestation) explanted for 3 days in a synthetic medium was measured every 24 h by radioimmunoassay. During the first day of explantation, the foetal testis produced, respectively, 1013 ± 132, 8734 ± 1118, 9179 ± 2185 and 3886 ± 309 (s.e.m.) pg/testis when explanted at 14½, 16½, 18½ and 21½ days respectively. Testosterone production by 13½-day-old testes was not detectable on the first day of culture, but appeared on subsequent days. Daily testosterone secretion increased on the 2nd and 3rd days of culture in 14½-day-old testes and decreased in older stages. These results suggest that the functional differentiation of the testis is independent of stimulatory factors like gonadotrophins. Dibutyryl cyclic AMP was found to stimulate testosterone production significantly from 14½ days of gestation onwards.

scholarly journals Influence of A23187 and dibutyryl cyclic AMP on progestagen production by rat granulosa cells in vitro

Reproduction ◽  
1989 ◽  
Vol 86 (1) ◽  
pp. 373-381 ◽  
Author(s):  
B. K. Tsang ◽  
D. F. Mattice ◽  
M. Li ◽  
E. K. Asem
Keyword(s):  
Cyclic Amp ◽  
Granulosa Cells ◽  
Dibutyryl Cyclic Amp

scholarly journals Isolation of cDNA clones for genes exhibiting reduced expression after differentiation of murine teratocarcinoma stem cells.

1984 ◽  
Vol 4 (10) ◽  
pp. 2142-2150 ◽  
Author(s):  
R A Levine ◽  
G J LaRosa ◽  
L J Gudas
Keyword(s):  
Stem Cells ◽  
Retinoic Acid ◽  
Cyclic Amp ◽  
Cdna Library ◽  
In Vitro Transcription ◽  
In Vitro Translation ◽  
Transcriptional Level ◽  
Cdna Clones ◽  
Dibutyryl Cyclic Amp

In the absence of retinoic acid, PSA-G teratocarcinoma stem cells spontaneously differentiate at a moderate frequency into fibroblast-like cells. In the presence of retinoic acid and dibutyryl cyclic AMP, PSA-G stem cells differentiate into parietal endoderm cells. We prepared a cDNA library from undifferentiated PSA-G teratocarcinoma stem cells; this cDNA library was then screened for gene sequences which exhibit a reduction in expression during the differentiation of these stem cells. From ca. 1,000 clones screened, eight independent sequences were isolated. The level of expression of these cloned genes decreases by 3.0-fold to more than 10-fold after differentiation of PSA-G cells into fibroblast-like cells. After treatment of either PSA-G or F9 teratocarcinoma cells with retinoic acid and dibutyryl cyclic AMP for 72 h, the expression of seven genes is inhibited by two- to fourfold. This decrease of clone-specific transcripts can be detected within 12 h after the addition of retinoic acid. Hybridization-selection and in vitro translation experiments identified the proteins encoded by three of the cloned genes: pST 6-23 codes for a 89,000-dalton protein, pST 7-105 codes for a 41,000-dalton protein, and pST 9-31 codes for a 34,000-dalton protein. The 89,000-dalton protein encoded by pST 6-23 is a heat shock protein. In vitro transcription experiments demonstrate that the retinoic acid-mediated decrease in pST 6-135- and pST 1-68-specific RNA occurs at the transcriptional level and that dibutyryl cyclic AMP acts posttranscriptionally to further depress the levels of these RNAs.

Tricarboxylic acid cycle activity in perfused rat lungs after O2 exposure

1992 ◽  
Vol 262 (4) ◽  
pp. L495-L501 ◽  
Author(s):  
D. J. Bassett ◽  
S. S. Reichenbaugh
Keyword(s):  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Enzyme Inactivation ◽  
Pyridine Nucleotides ◽  
Acid Cycle ◽  
Metabolic Conditions ◽  
Steady State Levels ◽  
14Co2 Production ◽  
Tricarboxylic Acid Cycle Intermediates

O2-induced impairment of mitochondrial energy generation was examined in intact lungs isolated from rats after 18-30 h exposure to either air or 100% O2 in vivo. Mitochondrial metabolic rates were determined by separate measurements of 14CO2 production from [1-14C]pyruvate and [U-14C]palmitate, perfused under normal and stimulated metabolic conditions brought about by perfusion with the uncoupler of oxidative phosphorylation, 2,4-dinitrophenol (DNP). In the absence of DNP, O2 exposure did not significantly alter 14CO2 productions from either substrate. DNP increased lung pyruvate and palmitate catabolism to CO2 twofold in air-exposed lungs but did not alter 14CO2 production in lungs isolated from O2-exposed rats. These data demonstrated an O2-induced impairment of maximal mitochondrial metabolism of both pyruvate and palmitate that could not be explained by alterations in tissue free coenzyme A or by loss of pyridine nucleotides. However, comparisons of the steady-state levels of tricarboxylic acid cycle intermediates between O2- and air-exposed lungs did identify isocitrate dehydrogenase as a possible site of O2-induced enzyme inactivation.

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